In the first year of this project, data were examined from 24 elderly subjects. The nocturnal sleep recordings revealed hidden sleep disorders in 11 of the subjects: nine had a sleep-related respiratory disturbance; two had a sleep-related movement disturbance, nocturnal myoclonus. These disturbances were associated with from 70 to over 200 brief arousals during sleep. Daytime evaluations showed that subjects with respiration disturbance during sleep were significantly sleepier than those whose respiration was undisturbed. Two subjects, whose daytime sleepiness was in the pathological range, were most severely affected by disturbed respiration. The third most sleepy subject had nocturnal myoclonus. These findings suggest that the sleep disturbance of the elderly often may be due to hidden sleep disorders and that these factors may contribute to impaired daytime alertness.